1. Technical Field
The present invention relates to a technology for reducing failure on display in a liquid crystal panel.
2. Related Art
Liquid crystal panels have a configuration in which one of a pair of substrates has pixel electrodes corresponding to respective pixels arranged in a matrix, the other substrate has a common electrode disposed so as to be common to all of the pixels, and a liquid crystal is sandwiched between each of the pixel electrodes and the common electrode. In such a configuration, when a voltage corresponding to a grayscale level is applied and held between each of the pixel electrodes and the common electrode, the orientational state of the liquid crystal is defined every pixel, and thus, the transmittance or the reflectance is controlled. Therefore, it can be said that in the configuration described above, only the component out of the electrical field acting on the liquid crystal molecules having a direction (or the opposite direction) from the pixel electrode to the common electrode, namely the direction perpendicular (vertical) to the surface of the substrate makes a contribution to the display control.
Incidentally, as the pixel pitch of the liquid crystal panel is narrowed due to miniaturization and improvement in definition, an electric field generated between the pixel electrodes adjacent to each other, namely the electrical field in a direction (lateral direction) parallel to the surface of the substrate, is generated, and further the influence thereof is becoming nonnegligible. When a lateral electrical field is applied to the liquid crystal to be driven by an electrical field in a vertical direction such as a vertical alignment (VA) liquid crystal or a Twisted Nematic (TN) liquid crystal, there arises a problem that orientation failure (reverse tilt domain) of the liquid crystal is caused to thereby cause failure on display.
In order for reducing the influence of the reverse tilt domain, there are proposed a technology (see, e.g., JP-A-6-34965, FIG. 1) of devising a structure of a liquid crystal panel such as to define the shape of the light blocking layer (an opening section) corresponding to the pixel electrode, a technology (see, e.g., JP-A-2009-69608, FIG. 2) of clipping the video signal equal to or higher than a set value when the average brightness value obtained from the video signal is equal to or lower than a threshold value under the determination that the reverse tilt domain is generated, and so on.
However, the technology of reducing the reverse tilt domain by the structure of the liquid crystal panel has disadvantages that the aperture rate is apt to be lowered, and that the technology is not applicable to the liquid crystal panels having already been manufactured without devising the structure. On the other hand, the technology of clipping the video signal equal to or higher than the set value has a disadvantage that the brightness of the image displayed is limited uniformly to the set value.